Diablo III is an upcoming dark fantasy/horror-themed action role-playing game developed by Blizzard, making it the third installment in the Diablo franchise. The game, which features elements of the hack and slash and "dungeon roaming" genres, was first announced on June 28, 2008, at Blizzard's World Wide Invitational in Paris, France.[2]

The game takes place in Sanctuary, the dark fantasy world of the Diablo series. This world was saved twenty years prior by a handful of unnamed heroes in Diablo II. Warriors that survived the onslaught of the armies of the Burning Hells have gone mad from their ordeals and it is up to a new generation of heroes to face the forces of evil threatening the world of Sanctuary. Players will have the opportunity to explore familiar settings such as Tristram.
The only confirmed NPCs are Deckard Cain,[5] who has appeared in both of the previous games, and his stepdaughter, a new character that accompanies the hero in quests from time to time. Cain's journal on the official site brings the player up to speed on the events of the first two games.[6] Diablo's world map is composed primarily of two main continents with several small islands in the Northwest region.[7]Diablo III is similar in style to its predecessor, Diablo II. The proprietary engine will incorporate Blizzard's custom in-house physics, a change from the original usage of Havok's physics engine,[8] and feature destructible environments with an in-game damage effect. The developers are aiming to make the game run on a wide range of systems, and have stated that DirectX 10 will not be required.[9]Diablo III will use a custom 3D game engine[10] in order to present an overhead view to the player, in a somewhat similar way to the isometric view used in previous games in the series.[9] Enemies will utilize the 3D environment as well, in ways such as crawling up the side of a wall from the depths into the combat area.[5]
As in Diablo II, multiplayer games will be possible using Blizzard's Battle.net service,[11] with many of the new features developed for StarCraft II also available in Diablo III.[9] Players will be able to drop in and out of sessions of co-operative play with others.[12]
An enhanced quest system, a random level generator, and a random encounter generator are slated for use in order to ensure the game provides different experiences when replayed.[2] Overall, the game will include both static and randomly generated levels.[12] Additionally, there will be class-specific quests to go along with the main storyline quests.[13] Blizzard originally planned to have in-game cutscenes,[14] but decided these would divert from the gameplay and decided against them. Two new armor pieces will be available: shoulder plates and leggings.[15]
Unlike previous iterations, gold can be picked up merely by touching it, rather than having to manually pick it up.[14] Sidekicks, unlike Diablo II, are now distinct NPCs who join the player, rather than randomly generated and endlessly replaceable hires.[14] One of the new features intended to speed gameplay is that health orbs drop from enemies, replacing the need to have a potion bar, which itself is replaced by a skill bar that allows a player to assign quick bar buttons to skills and spells; previously, players could only assign two skills (one for each mouse button) and had to swap skills with the keyboard. Players can still assign specific attacks to mouse buttons.[14]
Skill Runes, another new feature, are skill-modifying items that are randomly dropped by monsters and used across all classes. Similar to runes in Diablo II but instead of changing equippable items, they can be attached to skills as though they are items, often completely changing the gameplay of each skill.[16] They also have the ability to make one particular spell in each class more powerful, and give the player options as to how the rune will enhance a particular spell. For example, investing Skill Runes on the Wizard's "Lightning" can allow the players to make the lightning jump towards additional enemies, or, alternatively, adding the runes with explosion effect blows the enemy up and causes damage to the surrounding area.[17]

Got that from wikipedia, hopefully that's enough information. I'll post more if needed.
Anyone want to get this game other than me? Website here: http://us.blizzard.com/diablo3/

I am disappointed that Blizzard won't support LAN on this game. I was kinda disappointed when it happened to Starcraft 2, but I'm a bigger fan of the Diablo series. I'm seriously contemplating not buying it anymore because of that. The most fun I had on Diablo 2 was playing in a room with friends.